So I posted in GitHub regarding my problem, but so far no success in solving it. The reason I post here too is somebody may experience the same and maybe help to find a solution. Here are the details:
OS: Windows 10 Pro
IDE: VSCode and Atom (tried both, same result)
PlatformIO version: 3.5.0
After updating to this version, I can compile but cannot upload to my ESP 32 (Espressif ESP32 Dev Module).
Here’s my platformio.ini file:

My project stalls because of this error. Uploading via Arduino IDE is possible, but quite a pain as every time I decide to upload, have to rename my main.cpp to .ino, copy my whole file structure to the new folder (Arduino IDE requires the .ino to reside in its own folder), try to recompile the project and upload. And it was that easy with VSCode and PlatformIO. Hope this problem will be solved soon enough…

Sorry for duplicating this in both here and GitHub, but I really need this fix ASAP

I found the source of the error and managed to fix it. The reason for the error was Espressif32 Platform and especially version 0.11.0 (probably “Use new toolchain v1.22.0-75 for Arduino framework”). Downgrading to version 0.10.0 seems to fix my problem and now I’m able to upload again to my ESP32 Dev module.
Thank me for digging that deep, reinstalling VSCode, Atom, PlatformIO and everything that was possible…

Just FYI for anyone that visits this post in the future (as I have), platform/espressif32 had a patch release on Feb 8, 2018 in which they reverted the change to the new toolchain. This was then fixed in the next release, 0.12.0.